TTP and BRF proteins nucleate processing body formation to silence mRNAs with AU-rich elements. prevents formation of SGs. These findings identify HDAC6 as a central component of the stress response, and suggest that it coordinates the formation of SGs by mediating the motor-protein-driven movement of Goserelin individual SG components along microtubules. gene leads to embryonic lethality and growth retardation (Zekri et al. 2005). G3BP has attracted attention recently as it was found to increase decay of the c-Myc RNA and to localize to SGs (Tourriere et al. 2001, 2003). We show that HDAC6 is recruited to SGs and that pharmacological HDAC inhibition leads to impaired SG assembly. Indeed, HDAC6-deficient mouse embryo fibroblasts (MEFs) fail to form SGs, although they exhibit normal phosphorylation of eIF2 in response to stress. Furthermore, inactivating mutations in the catalytic domains or in the ZnF-UBP domain of HDAC6 impair SG assembly. Moreover, SG formation is abolished by disruption of microtubule arrays Rabbit Polyclonal to MASTL or by impairment of dynein motor proteins. We also found that HDAC6 is required for the cells to recover from oxidative Goserelin stress: In the absence of intact HDAC6 function, cells that have been treated with arsenite undergo apoptosis. Based on these results, we propose that HDAC6 is a central component of the stress response, regulating SG formation and potentially contributing to the control of RNA metabolism and translation. Results HDAC6 interacts with G3BP-1 in vivo and in vitro To identify novel proteins associating with HDAC6, we established a stable cell line expressing tagged HDAC6 (S-HDAC6-293) and used it for immunoprecipitations. Coprecipitating proteins were separated by SDS-PAGE and analyzed by mass spectrometry. By this approach, we identified G3BP as a prominent HDAC6-interacting partner. To verify the interaction between G3BP and HDAC6, coimmunoprecipitation and pull-down assays were established. As shown in Figure 1A, when HEK 293T cells were transiently cotransfected with constructs encoding epitope-tagged G3BP and HDAC6, the two proteins were found to efficiently coprecipitate, irrespective of the order. Interaction could also be evidenced in an in vitro binding assay, using a bacterially expressed GST-G3BP fusion protein and extracts from HDAC6-transfected HEK 293T cells or in vitro translated HDAC6 protein (Fig. 1B; data not shown). Importantly, interaction between Goserelin G3BP and HDAC6 could also be demonstrated with endogenous proteins from 293T cells, as shown in Figure 1C. The interaction is specific for HDAC6, as other HDACs, such as HDAC1 or HDAC4, fail to coimmunoprecipitate with G3BP (Fig. 1D). Taken together, these results indicate that G3BP is a bona fide novel specific interaction partner of the deacetylase HDAC6. Open in a separate window Figure 1. HDAC6 associates with G3BP. (= 3C4). (row. Bar, 10 m. The deacetylase activity of HDAC6 can regulate SG formation To identify the functional domain(s) of HDAC6 that direct the protein to SGs, expression vectors encoding tagged HDAC6 deletion mutants and G3BP were transiently cotransfected into HeLa cells, and the subcellular localization of these proteins was determined under control or oxidative stress conditions. The results are summarized and representative photomicrographs are presented in Supplementary Figure S2. All of the HDAC6 deletion mutants were localized in the cytoplasm, in agreement with our earlier results. Consistent with the immunoprecipitation results defining the interaction with G3BP, the full-length HDAC6 and deletion mutants containing at least one HDAC domain were recruited to SGs; in contrast, mutants containing only the N- or the C-terminal portion of HDAC6 failed to localize to SGs. Thus, either of the two HDAC domains is necessary and sufficient to direct HDAC6 to SGs. To examine whether the deacetylase activity of HDAC6 is required for SG formation, we first treated HeLa cells with the HDAC inhibitor, TSA, which inhibits all known HDACs, or with butyrate, which inhibits HDACs other than HDAC6 (Guardiola and Yao 2002). As shown in Figure 4, cells treated with TSA and arsenite exhibited a hyperacetylated microtubule network and formed fewer or no HDAC6-positive SGs. In contrast, treatment of the cells with butyrate did not prevent SG formation, suggesting that the deacetylase activity of HDAC6 might be important for formation of these structures. Open in a separate window Figure 4. The deacetylase activity of HDAC6 is critical for assembly of SGs. HDAC inhibition impairs formation of SGs. HeLa cells were control-treated or treated with 500 nM TSA or 5 mM Butyrate for 4 h prior to treatment with arsenite for 1 h and fixation. Double-immunostaining experiments were carried out with anti-Ac–tubulin and anti-HDAC6 antibodies, and analysis was done by confocal microscopy. Enlargements of boxed regions are.